1. Field of the Invention
This invention relates to a method and a furnace for disposal of steel-making waste such as dust caught by dust collecting equipment and slag (especially, slag containing CaO in a large quantity such as reducing slag, which will be described later), and an operating method for running the furnace very efficiently.
2. Description of the Prior Art
In the steel making by using an electric furnace or the like, dust generated from the furnace has been collected by equipping the dust collecting equipment in order to prevent air pollution.
The dust, that is steel-making waste is fine (1-5 .mu.m, for example) powder and contains FeO, Fe.sub.2 O.sub.3 (approximately 60%) and ZnO (approximately 15%), nevertheless it is difficult to be recycled, therefore it is the fact that the dust has been discarded without any treatment up to now.
In the steel making through the electric furnace, for example, oxidizing slag and reducing slag are exhausted as steel-making waste according to progression of steel refining.
Among them, the oxidizing slag, which is produced in an oxidizing period of steel making and exhausted after the oxidizing period, has been utilized as materials for road construction such as roadbed ballast of asphalt-surfaced roads and the like, however the reducing slag, which is produced in a reducing period and exhausted after the reducing period in the steel making, has no use in particular and has been discarded as it is.
Namely, the reducing slag contains free CaO in a large quantity as a chemical component, the free CaO changes into Ca(OH).sub.2 and expands cubically by absorbing water. Therefore, the reducing slag is not possible to be applied for the roadbed materials or so as it is, and has been discarded without being recycled.
In discarding the dust and the reducing slag, it is required to go to the expense of abandonment. Therefore, there is a problem since the abandonment of the steel-making waste of this kind causes an increase in the cost of steel making.